Answer:
7i+20j-31k
Explanation:
Given the vectors u (3,5,-8) and v (2,-5,7), they can also be written as;
u = 3i+5j-8k
v = 2i-5j+7k
To express the vector 3u - v in vector form, first let us find the vector 3u;
3u = 3(3i+5j-8k)
3u = 3(3i)+3(5j)-3(8k)
3u = 9i+15j-24k
Subtract v from the resulting vector.
Since v = 2i-5j+7k
3u - v = 9i+15j-24k - (2i-5j+7k)
3u-v = 9i+15j-24k -2i+5j-7k
collect the like terms
3u-v = 9i-2i+15j+5j-24k-7k
3u-v = 7i+20j-31k
Hence the vector 3u-v in the form v = vi+V2j+ v3k is 7i+20j-31k